一个简单的自定义web框架

只有一个servlet，这个servlet处理所有的*.do；

当有请求来时，根据请求的uri，选择对应的action进行处理；

action和uri使用注解来相互映射，中央控制的servlet在启动的时候就扫描classes目录下面的所有class文件，找出带有注解的类，并放入map中，key为uri的值，value为action对象；

需要自定义classloader来加载指定目录下的classes文件；

1.定义注解:

package com.oterman;

import java.lang.annotation.Retention;

import java.lang.annotation.RetentionPolicy;

@Retention(RetentionPolicy.RUNTIME)

public @interface Control {

     String value();

}

2.定义Action

package com.oterman;

@Control("/book" )

public class BookAction {

     

     /**

      * 默认执行该方法

      */

     public void exec() {

           System.out.println( "exec()....执行了哦" );

           System.out.println( this.getClass().getClassLoader());//com.oterman.MyClassLoader@3d637d45

          

     }

     public void add(){

           System.out.println( "add()....执行了哦" );

     }

     

     public void delete(){

           System.out.println( "delete()....执行了哦" );

     }

}

3.定义中央处理的ControllServlet,该servlet的映射为：

  <servlet >

    <servlet-name >ControllServlet </servlet-name>

    <servlet-class> com.oterman.ControllServlet</servlet-class >

  </servlet >

  <servlet-mapping >

    <servlet-name >ControllServlet </servlet-name>

    <url-pattern >*.do </url-pattern>

  </servlet-mapping >

ControllServlet.java

package com.oterman;

import java.io.ByteArrayOutputStream;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.util.HashMap;

import java.util.Map;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ControllServlet extends HttpServlet {

     private Map<String, Object> actionMap = null ;

     @Override

     public void init() throws ServletException {

           super.init();

           //中央处理servlet创建时，扫描classes目录下所有的class文件，找出action的class，并将 uri和对应的action放入到map中去；

           actionMap = new HashMap<String, Object>();

          String classpath = this.getServletContext().getRealPath("/WEB-INF/classes" );

          File dir = new File(classpath);

           try {

              scanClass(dir);

          } catch (Exception e) {

              e.printStackTrace();

          }

          

     }

     //判断一个文件是目录还是文件，如果是文件，判断是否为class文件，如果为class文件，判断是有注解！

     public void scanClass(File dir) throws Exception {

           if (dir.isDirectory()) {//为目录

              File[] files = dir.listFiles();

               for (File file : files) {

                   scanClass(file); //迭代操作

              }

          }

           if (dir.isFile()) {//为文件

               if (dir.getName().endsWith(".class" )) {

                    //将硬盘上的class文件读取为byte[];

                   FileInputStream fis = new FileInputStream(dir);

                   ByteArrayOutputStream bos = new ByteArrayOutputStream();

                    byte[] buffer = new byte[1024];

                    int len = 0;

                    while ((len = fis.read(buffer)) != -1) {

                        bos.write(buffer, 0, len);

                   }

                   bos.close();

                    byte[] bytes = bos.toByteArray();//class文件的字节码

                   

                    //自定义classloader，将byte[]翻译成class对象

                   MyClassLoader classloader = new MyClassLoader(this.getClass().getClassLoader());

                    Class clazz =classloader.getClass(bytes);

                   

                    //判断该类上是否有注解，如果有，则放入map中去；

                    Control annotation = ( Control) clazz.getAnnotation(Control.class) ;

                    if (annotation != null) {

                        String uri = annotation.value();

                         actionMap.put(uri, clazz.newInstance());

                   }

              }

          }

     }

     

     public void doGet(HttpServletRequest request, HttpServletResponse response)

               throws ServletException, IOException {

          

           //获取请求参数的 uri;

          String uri = request.getRequestURI(); // /MySimpleWebFrame/book.do

          String url = request.getRequestURL().toString();//http://localhost/MySimpleWebFrame/book.do

          

           //截取需要的uri；/book

          uri=uri.substring(uri.lastIndexOf( "/"), uri.lastIndexOf("." ));

          System. out.println(uri);

           //根据uri，查找map，得到处理请求的action

          Object action= actionMap.get(uri);

           if(action==null ){

               throw new RuntimeException("该请求没有对应的action！" );

          }

           //得到请求参数method,调用action相应的方法；

          String methodname=request.getParameter("method" );

           if(methodname==null){//如果请求参数没有改方法，则默认执行 exec方法！

              methodname= "exec";

          }

          Method method= null;

           try {

               method= action.getClass().getMethod(methodname, null);

          } catch (SecurityException e) {

              e.printStackTrace();

          } catch (NoSuchMethodException e) {

              e.printStackTrace();

               throw new RuntimeException("该action上没有"+methodname+ "方法！");

          }

          

           //调用该方法

           try {

               method.invoke(action, null);

          } catch (IllegalArgumentException e) {

              e.printStackTrace();

          } catch (IllegalAccessException e) {

              e.printStackTrace();

          } catch (InvocationTargetException e) {

              e.printStackTrace();

          }

          

     }

     public void doPost(HttpServletRequest request, HttpServletResponse response)

               throws ServletException, IOException {

          doGet(request, response);

     }

}

/**

 * 自定义类加载器，将byte[]加载为class对象

 * @author oterman

 *

 */

class MyClassLoader extends ClassLoader{

     //自定父加载器，按照加载机制进行加载！加载一个类时，都先交给父类加载，父类加载不了，才一级一级往下传！

     public MyClassLoader(ClassLoader parent) {

           super(parent);

     }

     public Class getClass(byte[] bytes){

          System. out.println("myclassloader2...." );

           return defineClass(null, bytes, 0, bytes.length);

     }

}